Series motor-control system



D. JAMES 1,724,404.

. SERIES 140103 CONTROL SYSTEM F'i led Deb. 24, 1927 INVENTOR HearDfimes.

ATTORNEY 1 Patented Aug. 13, 1929.

1,724,404 PATENT OFFICE.

HENLEY D. JAMES, OI EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, 'A CORPORATION OF 'PENNSYLVAN IA.

seams moron-coarser. SYSTEM.

Application filed December 24, 1927. Serial No. 242,302.

My invention relates generall .to a system of control for series motorsan particularly to regulating the speed of a series motor by connectinga section of the field winding 1n 5 parallel with the.armature.

In the operation of a series motor under certain conditions of load, itis often impossible to obtain the desired speed regulation of the motorsince the current drawn by '10 the armature also flows through theentire field winding. When a series motor is operated under very lightload or at no load, some precaution must be taken to prevent the motorfrom running away.

My invention provides a method of control for a series motor whereinthefield winding is divided into two separate sections, one of which isdisposed to be connected in series with the armature when operating inone direction and the other of which is disposed to be connected inseries with the armature when operating in the opposite direction.

In order to obtain the desired speed regulation, the portion of thefield winding not '25 connected in series with the armature may beconnected in series with a resistor and in parallel with the armature sothat the exc1tation-of the field may be varied and a stronger \field'obtained when the armatureis running at hi h speed than is possible withthe straig t series field winding. This change of field excitation makesit possible to limit the speed at which the machine will rotate under noload and also establishes a lower maximum speed. for operation underheavy loads.

The object of my invention, generally stated, is to provide a method ofcontrol for series motors that shall be simple and efiicientinoperation.

A more specific object of my invention is to provide a method ofcontrolling the speed of a series motor through a divided field winding.

A further object of my invention is to provide a method of connectingeither of two separate sections of a series field winding in series withthe armature in accordance with the direction of rotation of a motor andeither of which is adapted to be connected in parallel with the armaturewhen the other is connected in series with the armature Another objectof my invention is to pro wherein dynamic braking is accomplished vide asystem of control for a series motor through-a section of the fieldwinding other than that previously connected in series with thearmature.

Other objects of my invention will become apparent to those skilledin'the art when the following description is considered in conjunctionwith the accompanying drawing in which- Figure l is a schematic view ofcircuits and apparatus constituting a control system arranged inaccordance with this invention.

Fig. 2 is a simplified view illustrating the circuit connections of theapparatus illustrated in Fig. 1 when themotor is operating in onedirection; and

Fig. 3 is a simplified view illustrating the circuit connections of thesame apparatus when the motor is operating in the opposite direction.

In order to operate the motor 10 in the forward direction, it may beconnected across the supply mains 14 and 14 by means of the switches 11,12 and 13.

Since the switches 11, '12 and 13 are of the electromagnetic type, anenergizing circuit is 80 provided to .efi'ect their actuation. Thisenergizing circuit may be controlled at will by means of the push-buttonswitch 15 and, w len closed, extends from the positively energizedsupply line conductor 14 through the push-button switch 15, theoperating coil of the switch 12, conductor 27, the starting resistor 28,and switch 13, to the negatively energized conductor 14';

The switches 11, 12 and 13 are retained in their closedpositions afterthe release of the push-button switch 15 by a holding circuit which isestablished upon the closure of the switch 11. As shown, the interlock29 of the switch 11, in conjunction with the conductor 30, provides acircuit paralleling the pushbutton switch 15, Therefore, upon theclosure of the switch 11, a holding circuit is established throughinterlock 29, and the pushbutton switch may be released withoutinterrupting the supply of energy to theoperrating coils of the switches11, 12 and 13.

It is always desirable that the starting voltage of a motor be ofconsiderably less magnitude than the voltageon which the motor is tooperate continuously and the starting resistor 28 is provided to controlthe voltage. In operation, the resistor 28 is gradually cut out of themotor circuit by the successive operation of the switches 31, 32

and 33, each of which is disposed to short circuit a resistor section.The switches 31,

32 and 33 are each magnetically operated and arranged so that apredetermined interval of time elapses between the energization of theirrespective coils and the closure of their respective contact members.

The energizing circuit for the switches 31, 32 and 33 is closed upon theclosure of the switch 12 and remains closed as long as either ofswitches 12 and 19 is' retained in its closed position. Upon the closureof the switch 12, an energizing circuit for the coil of switch 33, tothe switch 31 is established which may be traced from the positivelyenergized conductor 14 through conductor 34, interlock 35 of switch 12,conductor 36, the operating coilof switch 31, to the negativelyenergized conductor 14'.

When the switch 31 is closed, an energizing circuit for the switch 321scompleted through the interlock 37 and may be traced from the energizedconductor 36. through interlock 37 carried by the switch 31, theoperating coil of switch to the negatively energized conductor 14. Uponthe closure of the switch 32, an energizing circuit for the switch 33 isestablished and extends from the energized conductor 36 through theinterlock 37, carried by the switch 31, interlock 38 carried by switch32, and the operating negatively energized conductor 14. -Since theswitches 31, 32 and 33 are arranged to operate in a predeterminedsequence, with an appreciable time interval betweenthe clos operations,the desired time delay in cuttlng out the starting resistor is effectedand the motor 10 will, at I no time, draw excessive starting currents.

If the motor 10 is operated under'an ex-' ceptionally light load, sothat it continues to accelerate, it is desirable that the field exci-.'tatio'fi be increased to prevent the -motor from running away and thisis accomplished through the closure of the switch 39 which tainable thanfunctions to connect. a section of the series field, winding 40 inparallel with the armature of the motor; If this section of the fieldwinding 40 is connected in parallel with the armature when the motor isoperating under heavy loads, a lower operating speed is obwas possiblethrough the use of the section 24 alone.- The circuit paral *leling thearmature which is completed through the switch 39 may be traced from thearmature oat motor 10, through resistor 41, the contact members66 ofswitch 39, conductor 42, conductor 43 and the field .winding 40 back tothe armature of-motor 10.

Y The ener izing circuit for the switch 39 is completed through theactuation of the manually operated switch 44 and extends from thepositively energized conductor 14, through conductor 45, interlock 46 ofthe switch 47, interlock 67 of switch in its open position, conductor48, the operating coil of switch-39, conductor 49, and the manpallyoperated switch 44, to the negatively energized conductor 14'.

When it is desired to stop the operation of the motor 10, thepush-button switch 17 is depressed, and the energizing circuit for theswitches 11, 12 and 13 is interriipted to permit the switches to open,

and the motor 10 to be disconnected from its source of supply.

If the switch 44 remains closed after the motor 10 has been disconnectedfrom its source of supply, dynamic braking is effected, since'the motor10 is short circuited. The braking circuit is established by the closureof the switch 39 and may be traced from the armature through resistor41, the contact member 66 of switch 39, conductor 42, conductor 43,field winding 40 returning to the armature-10. Therefore, the resistor41 serves as a braking resistor upon the discon nection of the motor 10from its source of supply, after being-operated in the forwarddirection. 1

When it is desired to operate themotor 10 in the reverse direction, thepush-button switch 56 is actuated to and an energizing circuit for themagnetically operated switches 47, 19 and 13 is established which may betraced from the positively energized conductor 14, through the itsclosed position,

push-button switch 56, the operating coil of switch 47, conductor 57,the operating coil of switch 19, the push-button switch 17, conductor 58interlock 59 of switch 12, conductor 20 an I the negatively energizedconductor 14'.

The motor 10 is connected to its source of supply upon the closure ofswitches 47,19 and 13, so that it operates in the reverse dimotion. Themain motor circuit in this case extends from the ductor 14. throughconductor 60, contact member 61 of switch field winding 40, the

armature of motor 10, conductor 62, contact member 63 of switch 47,conductor 43, the

the operating coil of switch 13, to

positively energized conv 19, conductor 27, the startin resistor 28 andthe contact members of switc 13 through the negatively energizedconductor 14'.

The holding circuit forthe switches 47, 19 and .13.is completed byestablishing a parallel to the push-button switch 56 through theinterlock 64 of switch 47, exactly as depath.

scribed in connection with the ush-button switch and the interlock 29 0switch 11.

Acceleration of the motor in the reverse direction is'acoomplished,through the opera: tion of switches 31, 32 and 33, to short circuittheir corresponding sections of the starting resistor 28, 1n the mannerdescribedin connection with the forward acceleration of the motor. Theenergizing circuit. for the switches 31, 32 and 3,3, 1n this case, iscompleted upon the closure of the interlock 65 of switch 19.

When it is desired to decrease the operatthe reversedirectiqn, theswitch '50 may be closed to connect the field winding 24 in parallelwithithe armature and thereby in crease the field excitation. Thecircuit parallelin the armature which is completed throug the switch50'may betraced from the armature of the motor 10, through resistor 55,contact members 69 of switch 50, conductor 54, conductor 23 and thefield winding 24 and back the armature of,

motor 10.

, The operation of the switch 50 is accom plished through the closureof'the manually operated switch '44 which completes the energizingcircuit for the electromagnetically operated switch 50, provided theswitches 11 and 39 are both in their open positions. The energizingcircuit for the switch '50 may be traced from the fositiyely 'ener izedconductor 14 by con uctor 51, inter 'ock52 of switch 11, conductor 53,the operating coil of switch 50, interlock'68 of switch 39, byconductor. 49, through the manually operated switch '44, to thenegatively energized conductor 14;

If the line switches 13, 19 and 47 are 0 ned and the switch 44 retainedin its c osed position,"the switch 50remains in its closed position anddynamic braking is effected. Thedynamic-braking circuit,;which isestablished under these conditions, may be traced from the armaturethrough field winding 24, conductor 23, conductor 54, contact member 69of switch- 50 and resistor and back to the armature -of motor. 10.Therefore, the resistor 55 is utilized as a braking resistor 'upon thedisconnection of the motor 10 from its source of power su ply afterbeingoperated in the reverse irection. g I Since it is realized thatvarious modifications of. this embodiment may bemade without departinfrom the spirit and scope of my invention, 1t is intended that theforegoing description shall be construed as illustrati 'e and'not in alimitingsense. I claim as my-invention:

- armature, sai

series field windings, one of said field windings being disposed to beconnected in series with the-armature of said motor for. operation inthe forward direction and in parallel with the armature for operationinthe reverse direction, the other of said field winding bein disposedto be connected in parallel wit the armature for operation in theforward direction and in series with the armature for operation in thereverse direction, and a plurality of resistors disposed to be connectedin series with the respective field winding sections when connected inparallel with the armature, said resistors and field windings whenconnected in seriesparallel circuit with the armature effecting dynamicbraking when the motor has been deenergized.

2. In combination, a source of power supply, a motor having an armatureand a seri'es field winding, 0

sections, means r connecting a resistor in "series with either sectionvof said field winding, means for connecting said resistor and sa dsection of the field winding in parallel wlth the armature, the othersection of said field winding being connected in series with thearmature winding, means for reversing the relative connections of thesections of the field winding therely eration of the motor, an means forconnect- ,ing one section of the field winding in series with a resistorand in parallel with the armature-to eflect dynamic braking upon themotor being disconnected from the source of 3; l n a motor controlsystem, in combination, a motor having an armature'and two series fieldwindings, resistors, means for connecting one of said series fieldwindings and one of'said resistors in series circuit relation and inarallel circuit relation to the parallel circuit, and connecting theother of said series field. windings in series circuit relation to theparallel circuit whereby operation of the motor in one direction isemitted, and means for. connecting'the other 'ofsaid series fieldwindingsand anotherresistor in series circuit relatIon*"'and in parallelwith comprising a plurality of connection constituting a reversing theop 7 the armature, said connection constitutin a parallel circuit toefi'ect' a reverse operation of the motor, and connecting said one fieldwinding in series circuit relation to the re verse-operation parallelcircuit. y

In testimony whereoffI have hereunto subscribed my name this'13th day ofDecem-- ."ber,192' Y H NRY DL JAMES;

